Im fairly interested in the stats behind this at a larger scale as well, such as, which versions are more preferred by people who also play other game types, etc. Example: Which version of D&D is most preferred by people who also enjoy FATE...things like that.
I think it is also interesting to see whats being played as opposed to what's being sold, given the recent comments from Paizo's CEO.
- I have left the retroclones out, because (again my OPINION only) they represent either a) a significant enough departure of the version of D&D they are based on (OSRIC for example, by combining features of old and new into the same game) that they do not follow in the DNA of said origin system or b) a more freehand approach in capturing the spirit of an edition they are based on rather than actually "being a descendant" of said system.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.